tcm_fc: Work queue based approach instead of managing own thread and event based mechanism

Problem: Changed from wake_up_interruptible -> wake_up_process and
wait_event_interruptible-> schedule_timeout_interruptible broke the FCoE
target.  Earlier approach of wake_up_interruptible was also looking at
'queue_cnt' which is not necessary, because it increment of 'queue_cnt'
with wake_up_inetrriptible / waker_up_process introduces race condition.

Fix: Instead of fixing the code which used wake_up_process and remove
'queue_cnt', using work_queue based approach is cleaner and acheives
same result. As well, work queue based approach has less programming
overhead and OS manages threads which processes work queues.

This patch is developed by Christoph Hellwig and reviwed+validated by
Kiran Patil.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Kiran Patil <kiran.patil@intel.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>

1 files changed, 2 insertions, 10 deletions

diff --git a/drivers/target/tcm_fc/tcm_fc.h b/drivers/target/tcm_fc/tcm_fc.h
index bd4fe21a23b..3749d8b4b42 100644
--- a/drivers/target/tcm_fc/tcm_fc.h
+++ b/drivers/target/tcm_fc/tcm_fc.h
@@ -98,8 +98,7 @@ struct ft_tpg {
         struct list_head list;          /* linkage in ft_lport_acl tpg_list */
         struct list_head lun_list;      /* head of LUNs */
         struct se_portal_group se_tpg;
-        struct task_struct *thread;     /* processing thread */
-        struct se_queue_obj qobj;       /* queue for processing thread */
+        struct workqueue_struct *workqueue;
 };
 
 struct ft_lport_acl {
@@ -110,16 +109,10 @@ struct ft_lport_acl {
         struct se_wwn fc_lport_wwn;
 };
 
-enum ft_cmd_state {
-        FC_CMD_ST_NEW = 0,
-        FC_CMD_ST_REJ
-};
-
 /*
  * Commands
  */
 struct ft_cmd {
-        enum ft_cmd_state state;
         u32 lun;                        /* LUN from request */
         struct ft_sess *sess;           /* session held for cmd */
         struct fc_seq *seq;             /* sequence in exchange mgr */
@@ -127,7 +120,7 @@ struct ft_cmd {
         struct fc_frame *req_frame;
         unsigned char *cdb;             /* pointer to CDB inside frame */
         u32 write_data_len;             /* data received on writes */
-        struct se_queue_req se_req;
+        struct work_struct work;
         /* Local sense buffer */
         unsigned char ft_sense_buffer[TRANSPORT_SENSE_BUFFER];
         u32 was_ddp_setup:1;            /* Set only if ddp is setup */
@@ -177,7 +170,6 @@ int ft_is_state_remove(struct se_cmd *);
 /*
  * other internal functions.
  */
-int ft_thread(void *);
 void ft_recv_req(struct ft_sess *, struct fc_frame *);
 struct ft_tpg *ft_lport_find_tpg(struct fc_lport *);
 struct ft_node_acl *ft_acl_get(struct ft_tpg *, struct fc_rport_priv *);